The present invention relates generally to devices for measuring the flow rate or pressure of a fluid in a conduit and more particularly to devices for making such measurements with respect to conduits conducting dirty gases (e.g. coke oven gas) or dirty liquids.
Typically, such devices comprise a cavity connected by a line to the conduit through which flows the fluid whose pressure is to be measured. The connecting line puts the cavity in fluid communication with the conduit and allows fluid from the conduit to enter the cavity. One wall of the cavity is a diaphragm, and the pressure of the fluid entering the cavity is exerted against the diaphragm which in turn is connected to pressure-measuring instruments to record the pressure exerted on the diaphragm by the fluid in the cavity.
Oftentimes it is necessary to measure the pressure in a dirty fluid, such as coke oven gas. These dirty gases contain foreign elements which, if they enter the cavity of the measuring device, could, in time, plug the cavity and interfere with the measuring function thereof. This, of course, is undesirable.